Spacer fabric and use thereof

ABSTRACT

A spacer fabric has two transversely spaced cloth layers. First spacer yarns bridge and transversely connect the cloth layers and are each formed by a core yarn and a helical wrapping made of metal or having a metallic layer. Second spacer yarns also bridge and transversely connect the cloth layers but are of different construction from the first yarns.

FIELD OF THE INVENTION

The present invention relates to a spacer fabric. More particularly thisinvention concerns a knitted spacer fabric and a use thereof.

BACKGROUND OF THE INVENTION

A typical spacer fabric comprises two usually substantially flat orplanar cloth layers and spacer yarns that transversely bridge andinterconnect the cloth layers. Some of the spacer yarns and optionallyeven all of the spacer yarns having a core made of a yarn and a spiralwrapping.

Spacer fabrics and, in particular, knitted spacer fabrics arecharacterized by a light, air-permeable structure, with spacer fabricsgenerally having an elasticity in the transverse direction of theirthickness as a result of spacer yarns that run between the two clothlayers. By virtue of these properties, knitted spacer fabrics are oftenprovided as a soft, elastic layer that enables air circulation inmattresses, upholstered furniture, garments, or shoes. A conventionalknitted spacer fabric is known from DE 90 16 062.

In addition to such conventional applications in the consumer sector,spacer fabrics and, in particular, knitted spacer fabrics are frequentlyalso used as technical fabrics for highly specialized applications. Forinstance, knitted spacer fabrics are also used in the automotiveindustry, for example for climate-controlled seats under the seatcovers, with knitted spacer fabrics allowing for good contour adjustmentdue to their cushioning properties and very good restorative behaviordespite the overall low weight per unit area. Knitted spacer fabrics arealso used for the interior lining of vehicles, and it is even possibleto use them over air bags through the introduction of local tear lines.The possible applications of knitted spacer fabrics are not limited tothe areas of ventilation and/or elastic support. For instance, it isknown from WO 2012/139142 to use knitted spacer fabrics for railwaysleepers for connecting a concrete body to a sleeper pad, the knittedspacer fabric being embedded partially in the concrete body and in thesleeper pad during the manufacture of the sleeper body, thus enablingthe especially reliable, permanent connection of these two elements.

Another known application is the provision of a heating or sensorfunction, for which purpose wires and, in particular, stranded wires areincorporated into the fabric structure. Corresponding configurations areknown from DE 19 903 070, DE 10 2008 034 937, and DE 10 2009 013 250.

According to DE 10 2015 114 778, a knitted spacer fabric is proposed forheating purposes in which conductive yarns of a flat knitted cloth layerare formed from a plastic multifilament yarn provided with a conductivecoating. The multifilament yarn has the advantage that, despite theconductive and, in particular, metallic coating of the individualfilaments, it still has relatively good flexibility, thus enablingprocessing in a knitting process. The conductive yarns are exposed in atleast the flat knitted layer that is usually facing a user.

Another highly specialized application of a spacer knitted fabric isknown from US 2008/20299854 that also discloses a spacer fabric with theabove-described features. A spacer fabric with two cloth layers andspacer yarns connecting the cloth layers is described, the spacer yarnshaving a core that is made of a yarn and a helical wrapping around thecore. The knitted spacer fabric is fire resistant to a certain extent.This property is achieved particularly by the fact that the core isenclosed and protected by the wrapping, for which purpose the wrappingis made of a sufficiently insulating material wound up tightly aroundits core yarn.

OBJECTS OF THE INVENTION

It is therefore an object of the present invention to provide animproved spacer fabric.

Another object is the provision of such an improved spacer fabric thatovercomes the above-given disadvantages, in particular that has a newfunctionality.

Another object is a preferred use of such a spacer fabric.

SUMMARY OF THE INVENTION

A spacer fabric has according to the invention two transversely spacedcloth layers. First spacer yarns bridge and transversely connect thecloth layers and are each formed by a core yarn and a helical wrappingmade of metal or having a metallic layer. Second spacer yarns alsobridge and transversely connect the cloth layers but are of differentconstruction from the first yarns.

In the context of the invention, a wrapping is thus provided in at leastthe first spacer yarns that is made of metal or at least has a metalliclayer. A spacer fabric is thus provided that is electrically andthermally conductive between the two cloth layers transversely, i.e. inthe direction of thickness. However, the spacer yarns are not providedwith a continuous sheath, which would lead to substantial stiffening. Inparticular, the wrapping can also be selected such that the spacer yarnscan still be processed easily during manufacturing of the spacer fabric,which is not the case with solid or stranded metallic wires. The core ofthe spacer yarns is formed by a yarn. In keeping with its generalmeaning, the term “yarn” refers in this context to monofilaments,multifilaments, or threads.

However, the core is especially preferably formed by a multifilamentyarn that is substantially softer and more flexible than a monofilamentyarn with the same fineness. Although the metallic or metal wrappingdoes not form a closed surface and is flexible, the metallic materialstiffens the composite first yarns. Particularly in this context, it canbe advantageous if the core is made of a multifilament yarn, even ifpoorer restorative properties are produced in terms of a compressionhardness as compared to a monofilament yarns.

According to a preferred embodiment of the invention, in order not toadversely affect the flexibility of the spacer yarns that are providedwith the wrapping and, beyond that, in order to achieve good functionalproperties, the wrapping is strip-shaped and has a width and a thicknesswith the ratio of the width to the thickness being at least 5:1.

Several embodiments of such a strip-shaped material are conceivable inprinciple. For example, the wrapping can be separated in the form of astrip from a thin foil or another strip stock. According to anespecially preferred embodiment of the invention, however, a wire isprovided that is flattened and thus formed into the flat strip. Such areshaping of a round wire that is usually flat at first is also referredto as flattening.

According to a preferred development of the invention, the wrapping canbe made of copper or have a layer of copper in the interest of goodthermal and/or electrical conductivity. Particularly in consideration ofmaterial costs, copper is preferable to more noble metals such as goldor silver, but these materials and other metals can also be used inprinciple within the scope of the invention.

In order to achieve long-term protection in the case of a wrapping thatconsists substantially of copper, a covering layer of tin can beprovided provides protection from corrosion while not impairing thethermal and/or electrical conductivity. In particular, it is alsopossible to flatten tin-plated copper wire as described above and thusto transform it into a strip-shaped material without removing ordamaging the tin coating.

As already explained above, the spacer yarns provided with the wrappingretain a high degree of flexibility, because the successive helicalturns can still be moved and, in particular, angled relative to oneanother.

According to a preferred embodiment of the invention, the wrappingcovers between 30% and 95% of the core yarn on its lateral surface,particularly between 40% and 80%. This degree of coverage provides goodflexibility on the one hand while also providing sufficient conductivityin terms of heat and/or electricity on the other hand.

It is assumed that, in the usual embodiment of a core made of abasically nonconductive polymeric yarn, not only the electricalconduction but also the heat conduction takes place substantially viathe wrapping, which is metallic or has at least one metallic layer.

It should also be noted in this regard that, due to the helical shape ofthe winding, the effective length to be considered for electricalconduction and heat conduction is substantially greater than the lengthof the spacer yarn itself. With a typical width and coverage of thewrapping, the length of wrapping in the unwound or rectified state isbetween 1.5 and 4, preferably between 2 and 2.5 times greater than thelength of the wrapped core yarn itself. The spacer fabric, which ispreferably embodied as a knitted spacer fabric, is surprisinglycharacterized by very good conductivity in terms of electricity andheat.

For example, the total thickness of the spacer fabric can be between 1mm and 20 mm, preferably between 2 mm and 10 mm. The core, which ispreferably made of multifilament yarn, preferably has a fineness ofbetween 50 dtex and 150 dtex.

As already explained above, the wrapping preferably is a strip in orderto be wound around the core in a helical manner with the smallestpossible thickness. In order to ensure sufficient stability on the onehand and good processability on the other hand, and in order to providethe desired conductive properties, the wrapping preferably has across-sectional area of between 200 μm² and 10,000 μm², especiallypreferably between 600 μm² and 40 μm².

The two flat cloth layers are not limited in their specific design.Preferably, the flat cloth layers are made of polymeric yarns and arealso preferably free of metal and thus electrically non-conductive andthermally insulating.

In an embodiment as a knitted spacer fabric, different laying patternsare possible, and openings can also be provided in the cloth layers,each of which is formed by a plurality of stitches.

Particularly if the cloth layers are made of nonconductive yarnsaccording to a preferred embodiment of the invention, it can beadvantageous if the spacer yarns are integrated into the cloth layers sothat they are exposed to or even protrude beyond the outer faces of thespacer fabric. At the same time, the fact that the wrapping of thespacer yarns results in a certain stiffening can also be advantageouslyexploited, so that they are less strongly angled in the stitchformation. In particular, the first spacer yarns provided with thewrapping can be adjusted in the same way through suitable selection ofthe core on the one hand and of the wrapping on the other hand, that thefirst spacer yarns still have good processability but also have acertain strength and rigidity at the same time.

In the context of the invention, both the first and the second spaceryarns can be provided with the wrapping in the manner described.

According to an alternative, preferred embodiment of the invention, thefirst spacer yarns have core yarns with helically wound wrapping, whilea second portion of the spacer yarns is provided without wrapping.

The proportion of the number of one of the spacer yarns to the totalnumber of the first plus the second spacer yarns in a given area istypically between 10% and 90%, preferably between 30% and 70%. Thesecond spacer yarns are especially preferably made of monofilament yarnin order to impart good elastic properties and good compression hardnessto the spacer fabric. In the context of such an embodiment, a functionaldivision then takes place between the first spacer yarns and the secondspacer yarns.

According to an embodiment of the invention, the spacer yarns can bedeformed after they are wrapped in order to stabilize the spacer yarnsprovided with the winding to some extent. As with the flattening of awire to form the wrapping, the yarns provided with the wrapping can beflattened between rolls prior to processing, i.e. particularly knitting,in which case the spacer yarns are given an approximately ovalcross-sectional shape. By virtue of such an oval, flatly pressed crosssection, the structure of the first spacer yarns is stabilized on theone hand and, on the other hand, the flexibility in the spacer fabricformed is reduced. In particular, this can prevent the spacer yarns fromtwisting or the wrapping from twisting relative to the core.

The spacer fabric according to the invention can be provided in anespecially advantageous manner as a heat-conduction layer, for bestservice as the preferred use with an electrical or electronic component.

The knitted spacer fabric is characterized by a particularly lightstructure, but good heat transfer is possible in the transversedirection of thickness. It is also of particular advantage that thespacer fabric is elastic in the direction of thickness. For example, thespacer fabric can also be used in gaps and cracks in order to allow heattransfer there.

Such an arrangement is advantageous particularly if electricalcomponents are to be cooled in a housing. For example, if rechargeablebatteries, motors, and other electrical components are placed in ahousing with an ohmic resistance, the spacer fabric can be used for heattransfer in such installation situations. Optionally, an adhesive, apaste, or the like can be used on the cloth layers for better fixationand/or contacting, it being possible even then for thicknesscompensation or thickness adjustment to be performed by the spaceryarns. Different gap dimensions due to production-related fluctuationscan be compensated for by the knitted spacer fabric in a particularlyadvantageous manner, and because of the low weight per unit areacompared to known designs, weight savings can often also be achieved.Especially for the described applications, the heat conduction issufficient despite the overall airy structure.

Finally, applications are also conceivable in which the cooling isimproved even further through ventilation of the spacer fabric, so thata cooling by convection or a cooling air flow then also occurs inaddition to the heat conduction via the thickness.

One specific application in which the advantages described above areespecially evident is for an electrical component fitted in a housing,in which case small gaps may remain due to assembly. The electricalcomponent can be a motor, a rechargeable battery module, an inverter, orthe like. In this context, it should also be noted that, particularlywith regard to the storage of electric current for mobile applicationssuch as electric vehicles or in connection with photovoltaic systems,increasing demand exists for corresponding electrical components, withweight minimization being desired particularly for mobile use.

BRIEF DESCRIPTION OF THE DRAWING

The above and other objects, features, and advantages will become morereadily apparent from the following description, reference being made tothe accompanying drawing in which:

FIG. 1 is a perspective view of a piece of a knitted spacer fabric orfabric according to the invention;

FIG. 2 is a larger-scale view of a detail of the fabric of FIG. 1;

FIG. 3 is a view of a short piece of a spacer yarn of the knitted spacerfabric according to FIG. 1 that is made of a yarn and a wrapping;

FIGS. 4a to 4c shows method steps for forming the spacer yarn of thisinvention; and

FIG. 5 is a schematic view of a rechargeable battery module in ahousing.

SPECIFIC DESCRIPTION OF THE INVENTION

FIG. 1 shows a spacer fabric in the form of a knitted spacer fabric withtwo cloth layers 1 and first and second spacer yarns 2 a and 2 b thatextend transversely between the planes of and connect the layers 1. FIG.1 and the detail view of FIG. 2 show that the spacer yarns 2 a and 2 bare configured differently. The first spacer yarns 2 a each have a core3 formed by a multifilament yarn and a helical wrapping 4 around thecore 3. The wrapping 4 is made of metal or has at least one metalliclayer.

It can already be seen from the detailed view of FIG. 2 that, ifdesired, good electrical conduction can also be achieved by the metallicwrapping 4 transversely, in the direction of thickness, the other spaceryarns 2 b are formed of polymeric monofilaments.

The different spacer yarns 2 a and 2 b extend similarly between the twocloth layers 1 and also are of a similar thickness. While themetal-wrapped first spacer yarns 2 a ensure good conduction of heat andelectricity, the second spacer yarns 2 b can provide the compressionhardness and elastic recovery that are typical of a spacer fabric andparticularly a knitted spacer fabric.

The exact configuration of the first spacer yarns 2 a provided with thesheath 4 can be seen from the sectional view of FIG. 3. In theillustrated embodiment, the core 3 is a multifilament yarn with forexample a fineness of 76 dtex. Polyethylene terephthalate isparticularly suitable as the material, but other typical materials suchas various polyolefins, polyamide, and the like can also be employed.

It can be seen from FIG. 3 that the wrapping 4 has a strip-shapedconfiguration with a width b and a thickness d, the ratio of the width bto the thickness d being at least 5:1. In the illustrated embodiment,the wrapping 4 is made of tinned copper, it being possible for aninitially circular-section tinned copper wire to be flattened in orderto form the strip-shaped configuration. Such a method step is shown byway of example in FIG. 4 a.

It is also apparent from FIGS. 2 and 3 that there is a gap between thesuccessive turns of the wrapping 4, 30% and 95% of the core beingcovered.

The helical wrapping 4 also has the effect that the effective length forheat conduction or electrical conduction of the wrapping 4 is greaterthan the length of the core. In the unwound state, the wrappings 4typically have a length that is 2 to 2.5 times greater than that of therespective core yarns 3. Despite this increased path length, very goodconduction of heat is observed overall.

For example, the wrapping can have a cross-sectional area of between 200μm² and 10,000 μm², particularly between 600 μm² and 4000 μm². Themultifilament yarn that is here provided as the core 3 can have 24 or 36filaments, for example.

FIG. 4b indicates how the core 3 of multifilament yarn can be providedwith the wrapping 4. Finally, FIG. 4c shows that the first spacer yarns2 a can also be flattened to some extent before the knitting process tostabilize their cross-sectional shape and wrapping.

The spacer fabric according to the invention is provided in anespecially advantageous manner as a heat conduction layer, it being alsooptionally possible for ventilation to take place through it. In thiscontext, the highly schematic representation of FIG. 5 shows thearrangement of a rechargeable battery module 5 in a housing 6, with thespacer fabric forming an intermediate layer 7 between the outer surfaceof the module Sand the inner surface of the housing 6. In particular,this spacer fabric as an intermediate layer 7 can be used to compensatefor a remaining gap between the rechargeable battery module 5 and thehousing 6. It should also be noted that the actual gap to be bridged canvary greatly due to manufacturing-related variations. Particularly inthis context, the invention offers the advantage that the spacer fabriccan be compressed when used as a heat conduction layer and also resetselastically to a certain extent. Such compensation is not possible witha thermally conductive paste or other compact media.

We claim:
 1. A spacer fabric comprising: two transversely spaced clothlayers; and first spacer yarns that bridge and transversely connect thecloth layers and that are each formed by a core yarn and a helicalwrapping made of metal or having a metallic layer.
 2. The spacer fabricdefined in claim 1, wherein the wrapping is formed of metallic striphaving a width and a thickness, a ratio of the width to the thicknessbing at least 5:1.
 3. The spacer fabric defined in claim 2, wherein thestrip is flattened wire.
 4. The spacer fabric defined in claim 3,wherein the wire is of copper or has a coating of copper.
 5. The spacerfabric defined in claim 2, wherein the strip is wound helically aroundthe core yarn and forms a plurality of spaced turns between which theyarn is exposed.
 6. The spacer fabric defined in claim 5, wherein thestrip covers 30% to 95% of the core yarn.
 7. The spacer fabric definedin claim 1, further comprising: second monofilament spacer yarns thatalso bridge and transversely connect the cloth layers but that are ofdifferent construction from the first yarns. wherein the second spaceryarns are monofilaments.
 8. The spacer fabric defined in claim 1,wherein the core yarn is a multifilament yarn.
 9. The spacer fabricdefined in claim 1, wherein the cloth layers and first and second spaceryarns are knitted.
 10. The spacer fabric defined in claim 1, wherein atotal thickness of the spacer fabric is between 1 mm and 20 mm.
 11. Thespacer fabric defined in claim 1, wherein the core yarn has a finenessbetween 50 dtex and 150 dtex.
 12. The spacer fabric defined in claim 1,wherein the wrapping has a cross-sectional area of between 200 μm² and10,000 μm².
 13. The spacer fabric defined in claim 1, wherein the firstspacer yarns have a cross-sectional shape that is not circular.
 14. Useof the spacer fabric of claim 1 as a heat conduction layer.
 15. The usedefined in claim 14, wherein the spacer fabric is connected to anelectrical component.
 16. The use defined in claim 14, wherein thespacer fabric is in a gap between a housing wall and the electricalcomponent.
 17. A method comprising the steps of: forming first yarns ofa multifilament nonconductive core yarn wrapped helically by aconductive and flexible metal strip; providing second monofilamentaryyarns; and knitting together the first and second yarns into a spacerfabric formed of two transversely spaced cloth layers largely formed ofthe second yarns and bridged by first spacer yarns formed by the firstyarns and by second spacer yarns formed by the second yarns.